Understanding SRAM High-Temperature-Operating-Life NBTI: Statistics and Permanent vs Recoverable Damage

Isolation of NBTI Stress Generated Interface Trap and Hole-Trapping Components in PNO p-MOSFETs

“…Note that the obtained E D value is consistent with molecular H 2 diffusion [33], while the ratio of E A /E D (= n) is also consistent with the prediction of R-D model. It is important to note that the obtained E D from UF-OTF is identical to that obtained from charge pumping measurements [9], the later being a direct estimator of ΔN IT 15 and therefore justifies the correctness of the separation procedure. To prove that the aforementioned observation is universal, Fig.…”

“…The following are assumed: 1) the measured ΔV T for all PNO samples consists of ΔV IT (= q.ΔN IT /CET , CET being capacitance equivalent thickness) and ΔV h (= q.ΔN h /CET ), although their magnitude and relative dominance are determined by N density and thickness of the gate insulator; 2) the ΔV h part saturates in less than 1 s for such thin insulators [3], [6], [7], and hence, its contribution to overall ΔV T is constant for longer (t > 1 s) stress time; and 3) the ΔV IT part at longer stress time (equals the overall measured ΔV T less constant ΔV h component) follows power-law dependence with n = 0.16, as observed by very long-time measurements [11], [12], [15] and also as predicted by a simple solution of R-D model with H 2 diffusion [29]. 9 Note that the procedure is different from [3], [6], and [16], where such separation was performed by assuming a long-time exponent of n = 0.25 (which is not consistent with E A of the extracted ΔV IT and ΔV h components, as discussed later).…”

“…3 Data measured at Texas Instruments [11], TSMC [12], and Freescale Semiconductors [15] show this trend, although data from ST Microelectronics [16] show much higher value of n ∼ 0.25. This paper would assume n ∼ 0.16 as the long term value.…”

“…It has been shown that N density at the Si/SiON interface [controlled by nitridation type-plasma or thermal, N dose, starting base oxide thickness, and postnitridation anneal (PNA)] strongly influences n, although a measured n value remains independent of stress E OX and T [10]. However, the value of n [∼0.12 for plasma nitrided oxide (PNO) processes, resulting in low Si/SiON N density that reduces further at higher N density] obtained using UF-OTF is always lower than the value (n ∼ 0.16) 3 obtained by very long-time measurements (albeit with slightly higher delay, although the recovery is expected to have minimal impact at very long stress time) [11], [12], [15]. The T independence of long-time n suggests Arrhenius-like T activation [1], [5], [7], and an earlier report of n as a linear function of T [17] has been shown to be an artifact of measurement delay [5].…”

Impact Analysis of NBTI/PBTI on SRAM VMINand Design Techniques for Improved SRAM VMIN

“…A number of works have dealt with the impact of NBTI and PBTI on SRAM operation [3][4][5][6]. The threshold voltage degradation due to NBTI and PBTI decreases cell stability, which will become even more serious when combined with device mismatches [5,6].…”